Insulator-support.



0'. L. PEIRCE, In.

INSULATOR SUPPORT.

APPLICATION FILED OCT. 15.1915.

Patented Dec. 5, 1916.

UNITED STATES PATENT OFFICE.

CHARLES L. PEIRCE, JR., 0F PITTSBURGH, PENNSYLVANIA, ASSIGNOR 0F ONE-HALF T0 HUBBARD 8: C01, 015' PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENN SYLVANIA.

Specification of Letters Patent.

INSULATOR-SUPPORT.

Application filed October 15, 1915. Serial No. 56,005.

To all whom it may concern Be it known that I, CHARLES L. Pnrnon, Jr., a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented certain new and useful Improvements in Insulator-Supports, of which the following is a specification.

My invention relates to insulator supports and contemplates improvements which adapt such structures particularly for high.

For such service porcelain insulators are now sion service. It has, therefore, been the used almost exclusively, but, because of the differences in shrinkage in different lots of clay, it is commercially impossible to produce such porcelain insulators with accurate threaded bores, and it is therefore impractical to screw thread such insulators directly to pins. Also because of the excessive mechanical strength required it is impractical to use resilient threaded pins or supports such as are used" in lighter and lower tenpractice for a number of years to use a separate thimble so shaped as to be readily cemented in the bore of a porcelain insulator and with a screw threaded interior to fit the upper threaded portion of a pin or support.

' Such thimbles have howeverbeen invariably made of cast iron and in-so producing them it is necessary that their side walls be made relatively thick in order to give the required strength.

film of cement between the thimble and the insulator bore sides should be at least g thick in order to securely hold the thimble in the insulator. The cast iron thimbles, in order to be of sufficient strength in an insulator of this bore, must have side walls at least thick. This means that with these dimensions the upper threaded end of the supporting pin can have a diameter of only of an inch, and such diameter does not give the necessary strength and the: pin will bend just below the insulator bore and the insulator will be ruptured. Attempts have been made to strengthen the structure as by increasing the diameterof the pin below its upper threaded end but all such .attempts have proved unsuccessful.

The object of my invention is to overcome the above drawbacks and deficiencies and I accomplish this by the use of a sheet metal thimble drawn from sheet steel which, for the heaviest service, need be only 3 thick, the thimble being drawn from a sheet metal blank and pressed or rolled to provide internal and external threading. With such thimble secured in an insulator'of 1% bore, the diameter of the threaded end of the supporting pin can be 11 5: instead of only a when the cast iron thimble is used, and this increased diameter gives a strength great enough to develop a resistance greater than the breaking strength of the insulator. Furthermore, the steel thimble made by dies is much cheaper than the cast iron thimble.

diameter toward an expanded base, so that the body is slightly tapered proportionate to the bending movements to which the pin will be subjected. In other words, the diameters are such that the pin has uniform strength throughout and will have no weak sections, the section just below the insulator bore bein as strong as other parts of the pin. It as also been discovered that the electrical qualities of a porcelain insulator gradually deteriorate when the insulator is applied directly to an unyielding metal pin or to an unyielding thimble, such as the ordinary cast-iron thimble. This is due to the constant expansion and contraction of the pin or thimble, such expansion and contraction being greater than that of the insulator and causing stresses in the porcelain structure. Although these stresses have never been great enough to actually disrupt the insulator, the molecular structure of the porcelain is eventually changed, and an in sulator which has been subjected to these stresses for a period of two or three years will break down under electrical stresses very much below those for which the insulator was originally designed and tested. A thin sheet metal thimble will of course expand and contract under changes of tempcrature but the force of expansion and contraction will be very much below the resistance of the insulator and will therefore cause no appreciable or injurious stresses. If, however, the insulator with the sheet metal thimble cemented therein is intimately threaded on to a pin, the powerful expansion and contraction of the pin will be communicated to the thimble and to the insulator.

Another object of my invention is therefore to provide for resilient and more or less yielding connection between the thimble and pin.

My improved construction and arrangement is clearly illustrated in the accompanying drawing in which Fig. 1 shows the pin in vertical elevation with its upper end partly in diametral section and the thlmble and insulator in vertical diametral section.

The pin p is preferably forged from steel and has threads at provided on its upper section a by rolling or otherwise. The diameter of this upper section a is preferably uniform and from below this threaded section the diameter is increased progressively to the base Z), and the sides a: of this base extend preferably about 45. Centrally from the base the bolt section 0 extends and has its lower end 6 threaded for the reception of a nut n.

In practice the bolt end 0 passes through ahole in the supporting cross arm and this cross arm is clamped between the base 6 and the nut n to securely hold the pin in vertical position. The thimble t is drawn integrally from thin sheet metal and is cylindrical and cup-shaped and the sides are rolled or pressed to provide external and internal threading f and g, the internal diameter of the thimble being such that it will thread on to the threaded end section a of the pin.

In practice the thimble is first secured in the bore of an insulator. As shown, it is secured in the insulator I which has the bore h of larger diameter than the thimble in order to leave space for cement material 8.

The insulator bore sides are preferably threaded to form cement retaining projections and depressions and the threaded exterior of the thimble likewise forms retaining projections and depressions for the coment so that the thimble will be securely anchored in the insulator independently of any irregularities in the insulator due to expansion or contraction. With this accurately formed sheet metal thimble in the insulator, the insulator structure can be readily threaded on to the pin end and the pin body being accurately dimensioned as to diameter below its threaded section u, the resulting conductor supporting structure is very strong and rigid and devoid of weak spots and will stand up without bending under any force less than that which would break the insulator itself. Furthermore, there is no dead material and weight, the distribution of metal being such that a minimum amount will give maximum and uniform resistance strength.

As already pointed out it has been found that if the thimble within the insulator has snug and unyielding connection with the pin threads the powerful expansion and contraction forces of the pin will be communicated through the thimble to the insulator and the insulator will be gradually weakened. I however provide resilient and more or less yielding connection between the thimble and pin. As shown, the threads on the pin are slightly narrower than the internal thread grooves of the thimble so that the thimbles will fit slightly loose on the pins. In the top of the thimble I then place a disk (Z of elastic or resilient material such as rubber, leather, cork, or the like, and then the insulator is screwed down on the pin until the disk (Z is compressed between the top of the pin and the thimble head. The screw threads on the thimble will then bear upwardly against the screw threads of the pin, but such engagement is yielding on account of the resilient disk. The pin is free to expand, but such expansion force will not find its way to the insulator but is expended in the further compression of the resilient disk. The thimble will of course expand and contract under temperature changes, but being so thin, the force of expansion and contraction thereof is much below the resistance of the insulator and therefore causes no appreciable stresses.

Having described my invention I desire to secure the following claims:

1. The combination with a supporting pin having a threaded end. an insulator structure having a threaded bore for receiving said threaded pin end, the threaded engagement being slightly loose, and resilient material between the bore end and the pin top.

2. In combination, a metal pin: having threads at its upper end, an insulator, a.

sheet metal thimble secured in the bore of In witness whereof, I hereunto subscribe said insulator and having interior threads, my name this 11th day of October, A. D. said thimble threads being adapted for 1915.

loose engagement with the pin threads, and CHARLES L. PEIRCE, JR. a disk of resilient material adapted to be Witnesses:

compressed between the thimble and the pin RICHARD M. KERSOHNER,

top. A. R. ROBITZEK.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. 0. 

